1. Field of the Invention
The present invention relates generally to a method of wiring semiconductor devices. More particularly, the present invention relates to wiring semiconductor devices through energy beam irradiation by supplying to the semiconductor devices a reactive gas which forms a conductive material constituting a wiring through energy beam irradiation.
2. Description of the Background Art
Conventionally known is a technique for repairing (making holes in a protection film, disconnection and connection of wirings) LSI chips on wafers or mounted in packages, this being a semiconductor process with a precision below the order of a micron, by using a focused ion beam (FIB). This technique is necessary for repairing a defective part or analyzing a defect. The method of connecting wirings includes decomposition of an adsorbed gas and deposition of the decomposed material on a surface, which is obtained by irradiating with a focused ion beam (FIB) a sample adsorbing a gas placed under a gas atmosphere of a certain type. The film deposited on the surface forms a wiring.
FIG. 11 is a schematic view showing an arrangement of a conventional LSI wiring apparatus. With reference to FIG. 11, the arrangement of the conventional LSI wiring apparatus will be described. The LSI wiring apparatus comprises an ion beam column 101 for emitting, focusing, and deflecting a focused ion beam, a sample chamber 102, a reactive gas nozzle 103 for feeding a reactive gas to a substrate 150 on which wirings are formed, and a sample stage 104 on which substrate 150 is placed. Ion beam column 101 comprises an ion source 110 including a liquid metal ion source or the like, a beam extracting electrode 111 for extracting an ion beam from ion source 110, an electrostatic lens 112 for focusing the ion beam extracted by beam extracting electrode 111, a beam blanking electrode 113 for turning on/off focused ion beam 110 focused by electrostatic lens 112 and a beam deflector 114 for deflection scanning of focused ion beam 100.
For the emission of focused ion beam 100 by ion beam column 101, first, a negative voltage is applied to beam extracting electrode 111 with respect to ion source 110 to emit an ion beam. The emitted ion beam is focused by electrostatic lens 112 to become focused ion beam 100. Beam deflector 114 directs the focused ion beam onto a desired position of substrate 150. Focused ion beam 100 is turned on/off by applying a voltage to beam blanking electrode 113 to largely deflect the beam.
FIGS. 12A to 12C are diagrams showing in three dimensions operations in a wiring forming process by using a conventional LSI wiring apparatus shown in FIG. 11. Referring to FIGS. 12A to 12C, conventional wiring forming operations will be described. As shown in FIG. 12A, wiring layers 150a and 150b comprising Al are formed apart from each other at a predetermined interval on substrate 150. In forming a connection wiring for connecting wiring layers 150a and 150b, tungsten hexacarbonyl [W(CO).sub.6 ], for example, is fed through reactive gas nozzle 103 (see FIG. 11) to a position at which the connection wiring should be formed. As shown in FIG. 12B, focused ion beam 100 shifts along the position on which connection wiring 151 should be formed while irradiating the same. Such operations eventually form connection wiring 151 as shown in FIG. 12C. The focused ion beam 100 is a Ga ion beam having energy of 20 KeV, a beam diameter of 1 .mu.m and a beam current of 3 nA, for example. The irradiation energy of focused ion beam 100 in use decomposes W(CO).sub.6 molecules adsorbed on substrate 150 surface, thereby depositing a W film (tungsten film) of about 1 .mu.m thickness on the portion irradiated by focused ion beam 100 with an ion beam radiation dose of 10.sup.18 /cm.sup.2.
As described above, a desired connection wiring 151 is formed by supplying a reactive gas to a position at which the desired connection wiring 151 should be formed and directing focused ion beam 100 thereto in the conventional LSI wiring apparatus.
While it is easy with such a conventional LSI wiring apparatus to a form a connection wiring connecting two adjacent wiring layers, it is difficult to form a connection wiring connecting a plurality of wiring layers at opposite sides with an intermediate wiring layer provided therebetween.
FIG. 13A is a plan view of a wiring layer explaining the problem of a conventional LSI wiring apparatus and FIG. 13B is a perspective view of the wiring layer shown in FIG. 13A. With reference to FIGS. 13A and 13B, for
connecting wiring layers 150a and 150b when wiring layers 150a, 150c and 150b are arranged as shown in these drawings, a connection wiring should be formed to cross over 150c, which is difficult to achieve by a conventional LSI wiring apparatus.
Therefore, conventionally proposed is the LSI wiring apparatus shown in FIG. 11 wherein an insulating reaction gas for forming an insulating pattern also can be supplied from reactive gas nozzle 103 in addition to a conductive gas for forming a connection wiring. That is, the technique involves forming a connection wiring crossing over a wiring layer with an insulating pattern formed between the wiring layer to be crossed over and the connection wiring. This technique is disclosed, for example, in Japanese Patent Laying Open No. 61-245553.
FIGS. 14A to 14C are diagrams explaining wiring forming operations of the conventional improved LSI wiring apparatus. With reference to FIGS. 14A to 14C, description is provided of a formation of a connection wiring between wiring layers 150a and 150b when wiring layers 150a, 150b and 150c are provided as shown in the drawings. That is, with the wiring layers arranged as shown in FIG. 14A, an insulating pattern 160 is formed by supplying a gas forming a insulating material through a reactive gas nozzle (not shown) onto wiring layer 150c and directing a focused ion beam (not shown) thereto as shown in FIG. 14B. Then as shown in FIG. 14C, supply of a reactive gas forming a conductive material and irradiation of a region between wiring layers 150a and 150b with a focused ion beam result in formation of a connection wiring 151 therebetween. In the conventional example of an improvement as described in the foregoing, when it includes three wiring layers, wiring layers at opposite sides are connected crossing over the intermediate wiring layer to form a connection wiring by supplying an insulating reactive gas onto the intermediate wiring layer to form an insulating pattern thereon. A connection wiring (an aerial wiring) for connecting the opposite side wiring layers formed on the insulating pattern results in a wiring crossing over a wiring layer without short-circuit.
The conventional improved LSI wiring apparatus, however, involves a complicated process for forming connection wirings i.e., the conventional example of an improvement requires additional process of forming an insulating film for an aerial wiring crossing over a wiring layer. In addition, two types of reactive gas are required, one for a connection wiring and the other for an insulation pattern. Furthermore, the reactive gas for an insulating pattern (SiO.sub.2) is silan (SiH.sub.4) which is harmful. The conventional example of the improvement has another problem that insulation of an insulating pattern formed between a connection wiring and a wiring layer is not sufficient. In other words, the insulation characteristic of the insulating pattern formed by a reactive gas by using a FIB deteriorates due to the effect of an impurity such as Ga in the order of one to two digits as compared with an ordinary SiO.sub.2 film.
Thus, while the conventional improved LSI wiring apparatus allows an aerial wiring connecting opposite side wirings crossing over an intermediate wiring layer when a plurality of wiring layers are arranged, the apparatus makes manufacturing steps complicated and the result may deteriorate an insulation characteristic of an insulating pattern formed for the aerial wiring.